This time our task was building the backend. Using Node.js/PostgreSQL we created it from scratch in collaboration with Brie's in-house team. Third-party APIs were connected. Among them is Taxjar for tax calculation and Stripe for payment processing. We carried out manual (smoke, regression, exploratory) testing of the backend part of the application using the "White Box" methodology (testing with access to the source code), which made it possible to predict defects and ask the necessary clarification questions to the project manager about the application in advance. We mainly used 2 tools: Postman for testing REST requests and DBeaver for database access and manipulation. For performance testing and optimization, the application was covered by internal load tests using Jmeter. The project manager's job was to: - make estimation analysis; - cooperate with the client to clarify requirements / update tasks / progress reports (calls / messenger); - draw up a roadmap of the project; - prepare the workspace in the task manager (Trello) for a productive process; - coordinate the work of the developer and QA; - monitor the implementation of tasks and compliance with deadlines.